Academic literature on the topic 'Adjustable boundary condition'
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Journal articles on the topic "Adjustable boundary condition"
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Khalid Ahmed, Nayaz, and Martin Hecht. "A boundary condition with adjustable slip length for lattice Boltzmann simulations." Journal of Statistical Mechanics: Theory and Experiment 2009, no. 09 (September 29, 2009): P09017. http://dx.doi.org/10.1088/1742-5468/2009/09/p09017.
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Hwang, W. M., and C. Z. Yu. "Optimal Synthesis of the Adjustable Knock-Out Cam-Follower Mechanism of a Bolt Former." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 219, no. 8 (August 1, 2005): 767–74. http://dx.doi.org/10.1243/095440605x31553.
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This paper presents a feasible method for improvements to the adjustable knock-out cam-follower mechanism of a bolt former. On the basis of the results of analysing an existing knock-out mechanism of a bolt former, the design requirements for a new mechanism are developed. In order to meet some specific requirements and that the displacement, velocity, and acceleration curves of the follower motion are continuous, the new cam profile consists of two circular arcs and a fifth-degree or sixth-degree polynomial segment. For the cam profile with a sixth-degree polynomial segment, besides the six specified boundary conditions, a variable condition is used as a design variable for the optimization design. The maximum strike velocity between the knock-out screw and knock-out pin for all knock-out strokes is minimized by using the golden section method. The kinematic characteristics of the new knock-out camfollower mechanism synthesized are better than those of the existing mechanism. The method presented is illustrated by an example.
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Samii, Ali, and Vahid Lotfi. "High-order adjustable boundary condition for absorbing evanescent modes of waveguides and its application in coupled fluid–structure analysis." Wave Motion 49, no. 2 (March 2012): 238–57. http://dx.doi.org/10.1016/j.wavemoti.2011.10.001.
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Herbert, Eric, Cyprien Morize, Aurélie Louis-Napoléon, Christophe Goupil, Pierre Jop, and Yves D’Angelo. "Buoyancy-driven destabilization of an immersed granular bed." Journal of Fluid Mechanics 843 (March 26, 2018): 778–809. http://dx.doi.org/10.1017/jfm.2018.141.
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Under suitable conditions, an immersed granular bed can be destabilized by local thermal forcing and the induced buoyant force. The destabilization is evident from the triggering and establishment of a dense fluid-like granular plume. Varying the initial granular layer average height $h$, a time series of the free layer surface is extracted, allowing us to dynamically compute the underlying volume of the granular layer. Different observed phenomena, namely the initial interface deformation, the lowering of the average granular interface (i.e. decrease of the granular layer volume) and the emission of a plume, are analysed. We show that the phenomenon is mainly driven by heat transfer, for large $h$ and also involves a variable height thermal boundary condition and Darcy flow triggering, for small $h$. Simple modelling with no adjustable parameters not only allows us to capture the observed scaling power laws but is also in quantitative agreement with the obtained experimental data.
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Ukita, Jinro, and Douglas G. Martinson. "An efficient adjustable-layering thermodynamic sea-ice model formulation for high-frequency forcing." Annals of Glaciology 33 (2001): 253–60. http://dx.doi.org/10.3189/172756401781818194.
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AbstractRecent observations suggest that high-frequency forcing events have profound influence on the air-sea-ice interactions in the polar region. Studying these events with sea-ice models requires close examination of the model sensitivity that may arise from the high-frequency variability of the forcing. We show that the maximum layer thickness is dictated by the time-scale of the forcing variability and that the computation of the surface temperature develops enhanced sensitivity at high-frequency forcing. We resolve these constraints by developing an "adjustable-layering" thermodynamic formulation for ice and snow that re-computes the number of layers required each time-step to satisfy this maximum thickness, which preserves the total enthalpy and general internal thermal gradients. The conservation equations form a tri-diagonal system ideal for a fast and efficient implicit solution. Furthermore, we resolve the issue of the high sensitivity of the surface flux balance by solving the linearized version of the flux boundary condition simultaneously with the overall conservation system. In this paper we develop the analyses specifying the model requirements, describe the model system and test its algorithmic implementation.
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Zhang, Jun, Xin Wu Zeng, Yi Bo Wang, Zhen Fu Zhang, and Dan Chen. "Numerical Simulation of the Buried Object Detection Based on Underwater Plasma Acoustic Source." Applied Mechanics and Materials 105-107 (September 2011): 80–83. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.80.
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Detection and classification of buried objects is of great importance in underwater counterterrorism and archaeology. To penetrate the sediment, a low frequency intensive acoustic source is needed. Underwater plasma acoustic source (UPAS) with high voltage discharge has the advantage of adjustable pulse length, high source level output and no pollution to the environment, which can satisfy these needs. In this paper, we introduced the UPAS, including its basic mechanism, structure and pressure output. Then we build up an elastic wave propagation model, solved it with finite difference and staggered grid methods, and combined with certain source and boundary condition, we simulated and analyzed the pressure wave propagation in time domain with an aluminum cylinder buried in sediment, from the results we validated the effectiveness of UPAS in the application of buried object detection.
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Sekularac, Milan, and Novica Jankovic. "Experimental and numerical analysis of flow field and ventilation performance in a traffic tunnel ventilated by axial fans." Theoretical and Applied Mechanics 45, no. 2 (2018): 151–65. http://dx.doi.org/10.2298/tam171201010s.
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To investigate air flow in longitudinally ventilated traffic tunnels, a scaled model of a typical road-traffic tunnel with an appropriate ventilation system based on axial ducted fans, is designed and built in the Lab. The focus of this paper is the airflow in a bi-directional traffic, two-lane tunnel. At the scale ratio of approx. 1:20, at 20.52m length it represents ? 400m of a realscale tunnel. The model consists of two parallel tunnel tubes, where the main tunnel (with a hydraulic diameter of ???1 ? 0.4m) has the geometry of a scaled road traffic-tunnel. The second tunnel (???2 ? 0.16m) has a smaller size and is circular in cross-section, used only to simulate airflow towards an evacuation tunnel tube. Thus the two tunnels are connected by the evacuation passages, equipped with adjustable escape doors. By a combination of experimental and numerical work, the air flow-field and the performance of the ventilation system are investigated. The velocity field and its turbulence properties exiting the fans were determined experimentally using hot-wire anemometry. These data were further processed to be used in the tunnel flow computations by CFD. The efficiency of momentum transfer (????, Kempf factor) of the longitudinal tunnel ventilation is determined. The effect that the imposed boundary conditions and the level of their detail, have within a CFD computation of tunnel airflow, with respect to accuracy, velocity distribution and computed ????. Finally a traffic-loaded (traffic ?jam?) case of flow is studied through experiment and CFD. The difficulty in assessing the required thrust of the plant in traffic-jam tunnel conditions is discussed, and the ventilation efficiency is estimated. Based on later results, the two limiting shapes of axial velocity distribution with respect to height above the road, in this type of tunnel and traffic, are estimated. The last result can be used as a realistic boundary condition (as inlet b.c. and/or initial condition) for numerical studies of flow and fire scenarios in such tunnels with the traffic load critical for design.
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Canuto, V. M., M. S. Dubovikov, M. Luneva, C. A. Clayson, and A. Leboissetier. "Mixed layer mesoscales: a parameterization for OGCMs." Ocean Science Discussions 7, no. 2 (April 29, 2010): 873–917. http://dx.doi.org/10.5194/osd-7-873-2010.
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Abstract. We derive and assess a parameterization of the mixed layer vertical and horizontal mesoscale fluxes of an arbitrary tracer. The results, which are obtained by solving the mesoscale dynamic equations and contain no adjustable parameters, are expressed in terms of the large scale fields resolved by coarse resolution OGCMs (ocean global circulation models). The new model can be put in the right perspective by considering the following. Thus far, the lack of a mixed layer mesoscale model that naturally satisfies the required boundary condition (the vertical flux must vanish at the surface), was remedied by extending the stream function modeled for the adiabatic deep ocean into the mixed layer using an arbitrary tapering function chosen to enforce the required boundary condition. The present model renders the tapering schemes unnecessary for the vertical flux automatically vanishes at the ocean surface. The expressions we derive for the vertical and horizontal mesoscale fluxes are algebraic and should be used in conjunction with any of the available mesoscale models valid in the adiabatic deep ocean. We also discuss a new feature representing the effect of sub-mesoscales on mesoscales. It is shown that in the case of strong wind, one must add to the mean Eulerian velocity that enters the parameterization of the mesoscale fluxes a new term due to sub-mesoscales whose explicit form we work out. The assessment of the model results is as follows. First, previous eddy resolving results indicated a robust re-stratification effect by mesoscales; we show that the model result for the mesoscale vertical flux leads to re-stratification (its second z-derivative is negative) and that it is of the same order of magnitude but opposite sign of the vertical flux by small scale turbulence, leading to a large cancellation. Second, since mesoscales act as a source of the eddy kinetic energy, we compare the predicted surface values vs. the Topex-Poseidon. Third, we carry out an eddy resolving simulation and assess both z-profile and magnitude of the model vertical flux against the simulation data. The tests yield positive results. A more stratified mixed layer has implication for the oceanic absorption of heat and CO2, a feature whose implications on climate predictions we hope to explore in the future.
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Wang, Hui Ping, and Qiao Jin. "Study of the Baseline Finite Element Model of a Cable-Stayed Bridge Based on the Field Inspection Data." Advanced Materials Research 243-249 (May 2011): 1908–16. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1908.
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For steel cable-stayed bridges which have been operating for many years, their static and dynamic parameters have been being changed because of corrosion and overloading. Therefore, an adjustable numerical model, describing and orienting all the various phases of the safety status of bridges, is needed for a theoretical guide of daily maintenance or periodical repair for them. In order to build such a model reflecting the different phases of working conditions of a bridge, a link between the model and the present condition of the targeted bridge should be erected by periodical field inspections for the structure. In this paper, backed on a practical engineering example, the Shengli cable-stayed bridge of Dongying, a finite element model (FEM) based on the periodical field inspection data was proposed, which could possess a strategy modified correspondingly according to parts or all of the results in the field inspections. Specifically, for the initial FEM, three important issues in the modeling of such a complicated bridge, such as simulation of boundary conditions, equivalence of orthotropic steel deck, and implementation of accurate cable tensions, were firstly studied. Then, the initial finite element model built was modified in terms of the optimization principle by minimizing the difference between the static deflections resulting from the field inspection and those calculated by the FEM before being modified. Lastly, dynamic results from the field inspection were compared with those from the optimized FEM to justify feasibility and reasonability of the developed three-dimension FEM which could reflect one or some certain properties of the structure we were emphatically paying attention to. This model-building and model-modifying method for the baseline FEM of the Shengli cable-stayed bridge also provided reference for the similar existing cable-stayed bridges.
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Schulz, M. "Non-spherical source-surface model of the heliosphere: a scalar formulation." Annales Geophysicae 15, no. 11 (November 30, 1997): 1379–87. http://dx.doi.org/10.1007/s00585-997-1379-1.
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Abstract. The source-surface method offers an alternative to full MHD simulation of the heliosphere. It entails specification of a surface from which the solar wind flows normally outward along straight lines. Compatibility with MHD results requires this (source) surface to be non-spherical in general and prolate (aligned with the solar dipole axis) in prototypical axisymmetric cases. Mid-latitude features on the source surface thus map to significantly lower latitudes in the heliosphere. The model is usually implemented by deriving the B field (in the region surrounded by the source surface) from a scalar potential formally expanded in spherical harmonics, with coefficients chosen so as to minimize the mean-square tangential component of B over this surface. In the simplified (scalar) version the quantity minimized is instead the variance of the scalar potential over the source surface. The scalar formulation greatly reduces the time required to compute required matrix elements, while imposing essentially the same physical boundary condition as the vector formulation (viz., that the coronal magnetic field be, as nearly as possible, normal to the source surface for continuity with the heliosphere). The source surface proposed for actual application is a surface of constant F̃ ≡ r-kB̃, where r is the heliocentric distance and B̃ is the scalar magnitude of the B field produced by currents inside the Sun. Comparison with MHD simulations suggests that k ≈ 1.4 is a good choice for the adjustable exponent. This value has been shown to map the neutral line on the source surface during Carrington Rotation 1869 (May–June 1993) to a range of latitudes that would have just grazed the position of Ulysses during that month in which sector structure disappeared from Ulysses' magnetometer observations.
Dissertations / Theses on the topic "Adjustable boundary condition"
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Issa, Nader. "Modes and propagation in microstructured optical fibres." University of Sydney. Physics and Optical Fibre Technology Centre, 2005. http://hdl.handle.net/2123/613.
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Microstructured optical fibres (MOFs), also commonly called photonic crystal fibres or holey fibres, describe a type of optical fibre in which continuous channels of (typically) air run their entire length. These `holes' serve to both confine electromagnetic waves within the core of the fibre and to tailor its transmission properties. In order to understand and quantify both of these functions, a new computational algorithm was developed and implemented. It solves for the eigenvalues of Maxwell's wave equations in the two-dimensional waveguide cross-section, with radiating boundary conditions imposed outside the microstructure. This yields the leaky modes supported by the fibre. The boundary conditions are achieved exactly using a novel refinement scheme called the Adjustable Boundary Condition (ABC) method. Two implementations are programmed and their computational efficiencies are compared. Both use an azimuthal Fourier decomposition, but radially, a finite difference scheme is shown to be more efficient than a basis function expansion. The properties of the ABC method are then predicted theoretically using an original approach. It shows that the method is highly efficient, robust, automated and generally applicable to any implementation or to other radiating problems. A theoretical framework for the properties of modes in MOFs is also presented. It includes the use of the Bloch-Floquet theorem to provide a simpler and more efficient way to exploit microstructure symmetry. A new, but brief study of the modal birefringence properties in straight and spun fibres is also included. The theoretical and numerical tools are then applied to the study of polymer MOFs. Three types of fibres are numerically studied, fabricated and characterised. Each is of contemporary interest. Firstly, fabrication of the first MOFs with uniformly oriented elliptical holes is presented. A high degree of hole ellipticity is achieved using a simple technique relying on hole deformation during fibre draw. Both form and stress-optic birefringence are characterized over a broad scaled-wavelength range, which shows excellent agreement with numerical modelling. Secondly, an analysis of leaky modes in real air core MOFs, fabricated specifically for photonic band gap guidance, is then used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, weakly influenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent confinement loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres. Finally, highly multimode MOFs (also called `air-clad' fibres) that have much wider light acceptance angles than conventional fibres are studied. An original and accurate method is presented for determining the numerical aperture of such fibres using leaky modes. The dependence on length, wavelength and various microstructure dimensions are evaluated for the first time for a class of fibres. These results show excellent agreement with published measurements on similar fibres and verify that bridge thicknesses much smaller than the wavelength are required for exceptionally high numerical apertures. The influence of multiple layers of holes on the numerical aperture and capture efficiency are then presented. It shows that a substantial increase in both these parameters can be achieved for some bridge thicknesses. Simple heuristic expressions for these quantities are given, which are based on the physical insight provided by the full numerical models. The work is then supported by the first fabrication attempts of large-core polymer MOFs with thin supporting bridges. These fibres exhibit relatively high numerical apertures and show good agreement with theoretical expectations over a very wide scaled-wavelength range.
Book chapters on the topic "Adjustable boundary condition"
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Thananjeyan, Brijen, Ashwin Balakrishna, Ugo Rosolia, Joseph E. Gonzalez, Aaron Ames, and Ken Goldberg. "ABC-LMPC: Safe Sample-Based Learning MPC for Stochastic Nonlinear Dynamical Systems with Adjustable Boundary Conditions." In Algorithmic Foundations of Robotics XIV, 1–17. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66723-8_1.
Full textConference papers on the topic "Adjustable boundary condition"
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Chen, Hao, Jiabing Wang, and Kun Yang. "Analysis of the Momentum Transport Boundary Conditions at a Fluid-Porous Interface." In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7395.
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The porous composite system is consists of porous medium and free fluid layer, which has extensive industrial applications. The study method for the flow field in the porous composite system includes the microscopic, mesoscopic and macroscopic approaches. When the two-domain approach is adopted, which is one of the macroscopic methods, the momentum transport boundary conditions at the interface between porous medium and free fluid layer is essential to analyze the flow field in the system. When Darcy equation is adopted to describe the flow in porous region, the Beavers-Joseph (BJ) interface condition can be used. When Darcy-Brinkman equation is adopted to describe the flow in porous region, the stress-jump (Ochoa-Tapia & Whitaker: OTW) interface condition can be used. To utilize these interface conditions, the velocity slip coefficient used in the BJ interface condition and the stress-jump coefficient used in the OTW interface condition should be specified. In this paper, a brush configuration is approximately treated as the equivalent porous media in the composite system. A numerical simulation method is used to obtain the microscopic solution for the flow in the system based on the Navier-Stokes equation applied in whole system, and an analytical method is used to obtain the corresponding macroscopic solution based on the two-domain approach. By comparing the microscopic and macroscopic solutions, the velocity slip coefficient and the stress-jump coefficient are determined since they can be treated as adjustable parameters. The influence of different flow types, including Poiseuille flow, Couette flow, and free boundary flow, are investigated. Also the impact of free fluid layer thickness and porous structure on the velocity slip coefficient and the stress-jump coefficient are discussed. The results indicate that, the velocity slip coefficient and the stress-jump coefficient are not only the parameters which depend on the porous structure, but also depend on the thickness of free fluid layer and flow type. When the thickness of free fluid layer is lower than a certain value, the impact of free fluid layer thickness on the velocity slip coefficient and the stress-jump coefficient is much obvious. In addition, when the thickness of free fluid layer is small, these coefficients are found to be dependent on the flow type. However, when the thickness of free fluid layer is large, the stress jump coefficient is independent of the thickness of free fluid layer and the flow type. Thus the stress jump coefficient obtained for a specific case can be used to predict velocity for different flow types and different thickness of free fluid layers.
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Saidimanesh, Mahdi, Azin Shahiri, and Ali Nikparto. "Simulation and Optimization of a Semi Spherical Air Bearing." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87334.
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It is important to test the attitude control systems on satellites before they are launched in space. Traditionally this has been done by dropping the satellite, and firing the thrusters before the satellite makes a soft landing in a net. This method only allows a few seconds of testing and does not lend itself to the measurement of pointing accuracy. A better method is to mount the satellite on a spherical air bearing. In this paper behavior of a semi spherical air bearing is studied and analyzed in various conditions. These bearings are used in different applications such as simulation of approximately frictionless condition which is the satellite’s situation in space. In this analysis FLUENT 6.3.26 is used to simulate the air bearing’s behavior. Simulation process is divided into 5 sections. These sections are accordingly 2dimensional with static boundary condition, 3dimensional and static, 2dimensional and dynamic and 3dimensional and dynamic boundary conditions. At last bearing’s function was optimized by changing some adjustable parameters which are important in controlling the bearings behavior such as air entering nozzles diameter and their number and location. Importance of this study is to simulate the behavior of the bearing in dynamic boundary condition using dynamic mesh. Eventually results of the simulation are compared to the actual test results and bearing behavior is analyzed. Finally best arrangement for achieving maximum normal load is studied.
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Nutakor, Charles, R. Scott Semken, Janne E. Heikkinen, Jussi Sopanen, and Aki Mikkola. "Layered Sheet-Steel Damping Estimation Using Optical Vibrometry." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46867.
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A non-contact modal analysis method is implemented to estimate the structural damping ratios for four stacks of sheet-steel, each bound using a different method. The setup comprised the four subject stacks and, for comparison, two single homogeneous steel plates of the same length and width with thicknesses that approximated the layered stack heights. To carry out the modal analyses, each test item was hung to simulate a free-free boundary condition. A force and frequency adjustable impact hammer imparted transient vibration to each hanging test piece after which the local relative velocity for each one of an array of discrete target points across the entire length-to-width surface was measured using an optical transducer. Damping ratios were extracted from the frequency response curves using the half power bandwidth method. Comparing the results obtained for the layered sheet-steel stacks with those from the homogeneous steel plates showed that damping ratios and loss factors can be estimated using the proposed experimental technique. The consistent impacts and the elimination of test structure mass loading improves the accuracy of damping estimates. In comparison to the solid plates, the layered sheet-steel stacks were characterized by increased damping. The effect was most significant for the stack bound together by polymer rivets.
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Bhat, Praveen, Satish Shenoy B, and Raghuvir Pai. "Elastohydrodynamic Lubrication Analysis of a Radially Adjustable Partial Arc Bearing Using Fluid Structure Interaction." In ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44479.
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Conventional method of performing Elasto-hydrodynamic Lubrication (EHL) analysis on a partial arc bearing involves simplification of actual physical model and developing complex codes. This paper presents the overall EHL analysis of a radialy adjustable single 60° partial arc bearing using the sequential application of Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD). Here the coupled field analysis uses the capabilities of commercially available Finite Element Software ANSYS/FLOTRAN and the technique of Fluid Structure Interaction (FSI). The pressure field has been obtained using CFD considering the flow to be laminar. Stress distribution and deformation in the pad due to resulting pressure force is obtained using Finite Element Method (FEM), satisfying the boundary conditions. The stress distribution indicates the critical points in the pad. In this paper the static characteristics of radialy adjustable single 60° partial arc bearings are predicted for different eccentricity ratios and length to diameter (L/D) ratios. The results show reasonable agreement in general.
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Zhang, X. Y., H. Zhang, and M. Zhu. "Experimental Investigation of Thermoacoustic Instabilities for a Model Combustor With Varying Fuel Components." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45783.
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In this study, a combustion facility was constructed that includes a flexible fuel supply system to produce synthesis gas using a maximum of three components. The rig with lean premixed burner is able to operate at up to 5 bars. The length of the inlet plenum and the outlet boundary conditions of the combustion chamber are adjustable. Experiments were carried out under a broad range of conditions, with variations in fuel components including hydrogen, methane and carbon monoxide, equivalence ratios, thermal power and boundary conditions. The dynamic processes of self-excited combustion instabilities with variable fuel components were measured. The mechanisms of coupling between the system acoustic waves and unsteady heat release were investigated. The results show that instability modes and flame characteristics were significantly different with variations in fuel components. In addition, the results are expected to provide useful information for the design and operation of stable syngas combustion systems.
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Tekes, Ayse, Kevin McFall, Franklin Woods, and Alexander Bryant. "Adjustable Compliant Mechanism Load Deflection Test Bench Design." In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-8943.
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Two adjustable compliant mechanism load deflection test benches are presented in this study. Both test bench mechanisms enable testing the deflection of flexible links or mechanisms. The modularity of the designs provides to test various link forms such as fixed-fixed and pinned-pinned joints. The load deflection test benches consist of a linear actuator, an amplifier rod, a linear rail and a sliding car. The measurement setup is equipped with force and displacement sensors for the linear actuator, various clamps to attach the compliant member, and machine vision software to measure member deflection. A displacement-controlled loading using a linear actuator, rack-pinion attached to a motor, or step loading with a pulley can be applied as an input to the system. There are several limitations involved in the design. First, the length of the test object should be kept between 5 cm to 30 cm. Second, a low cost linear actuator with a low extension velocity to obtain quasi static deflection curves of the compliant members is required. Finally, the design should also have the capability of providing various types of boundary conditions with interchangeable attachments. The force can be applied either parallel or perpendicular to the test object. Input load deflection is measured with the displacement sensor, and the resulting member displacement measured visually using machine vision software. This software synchronizes data from the displacement sensor and a calibrated camera image to automatically detect deflection using a pinhole camera model and known dimensions of the test apparatus. The purpose of this study is to design and fabricate a load deflection test setup capable of testing flexible links and compliant mechanisms. Two different designs are proposed and explored in this study. The first design is the modification of a commercially available ECP Model 210 educational turnkey system favorably utilized in undergraduate level vibrations and control labs. By attaching the designed clamps on two carts, fixed-fixed and U shaped compliant link load deflection can be obtained. Four cases such as fixed-fixed buckling beam, U shaped beam buckling with one end sliding, already buckled beam loaded at its upper midpoint, and inverse U-shaped beam loaded at its apex to form deflected M beam (with design 2) are considered. In order to achieve buckled beam experiments in which the load is applied at the midpoint of the already buckled links, a new test bench consisting of a linear actuator, rigid links, rail and two sliding cars is designed.
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Eichler, Christian, and Thomas Sattelmayer. "Experiments on Flame Flashback in a Quasi-2D Turbulent Wall Boundary Layer for Premixed Methane-Hydrogen-Air Mixtures." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23401.
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Premixed combustion of hydrogen-rich mixtures involves the risk of flame flashback through wall boundary layers. For laminar flow conditions, the flashback mechanism is well understood and is usually correlated by a critical velocity gradient at the wall. Turbulent transport inside the boundary layer considerably increases the flashback propensity. Only tube burner setups have been investigated in the past and thus turbulent flashback limits were only derived for a fully-developed Blasius wall friction profile. For turbulent flows, details of the flame propagation in proximity to the wall remain unclear. This paper presents results from a new experimental combustion rig, apt for detailed optical investigations of flame flashbacks in a turbulent wall boundary layer developing on a flat plate and being subject to an adjustable pressure gradient. Turbulent flashback limits are derived from the observed flame position inside the measurement section. The fuels investigated cover mixtures of methane, hydrogen and air at various mixing ratios. The associated wall friction distributions are determined by RANS computations of the flow inside the measurement section with fully resolved boundary layers. Consequently, the interaction between flame back pressure and incoming flow is not taken into account explicitly, in accordance with the evaluation procedure used for tube burner experiments. The results are compared to literature values and the critical gradient concept is reviewed in light of the new data.
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Ivanova, Elizaveta, and Gregory M. Laskowski. "LES and Hybrid RANS/LES of a Fundamental Trailing Edge Slot." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25906.
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This paper presents the results of a numerical study on the predictive capabilities of Large Eddy Simulation (LES) and hybrid RANS/LES methods for heat transfer, mean velocity, and turbulence in a fundamental trailing edge slot. The geometry represents a landless slot (two-dimensional wall jet) with adjustable slot lip thickness. The reference experimental data taken from the publications of Kacker and Whitelaw [1] [2] [3] [4] contains the adiabatic wall effectiveness together with the velocity and the Reynolds-stress profiles for various blowing ratios and slot lip thicknesses. The simulations were conducted at three different lip thickness and several blowing ratio values. The comparison with the experimental data shows a general advantage of LES and hybrid RANS/LES methods against unsteady RANS. The predictive capability of the tested LES models (dynamic ksgs-equation [5] and WALE [6]) was comparable. The Improved Delayed Detached Eddy Simulation (IDDES) hybrid method [7] also shows satisfactory agreement with the experimental data. In addition to the described baseline investigations, the influence of the inlet turbulence boundary conditions and their implication for the initial mixing layer and heat transfer development were studied for both LES and IDDES.
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Moita, A. S., A. L. N. Moreira, and Ilia V. Roisman. "Heat Transfer During Drop Impact Onto a Heated Solid Substrate." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23202.
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The present paper addresses the theoretical and experimental study of a liquid drop impacting onto a solid heated substrate. The experiments encompass the measurement and evaluation of the instantaneous substrate and contact temperatures, for different impact conditions and various thermodynamic properties of the liquid and target. Initial surface temperatures are varied from the ambient temperature up to slightly above the boiling temperature of the liquids (TW0max = 120°C), for different surface materials, covering significantly different wall effusivities, thus allowing to validate the model for extreme conditions. The theory is based on the remote self-similar analytical solution of the Navier-Stokes equations in the spreading drop coupled with the energy equation, which allows obtaining a theoretical solution for the flow field and temperature field in the liquid region. An explicit analytical expression is proposed for the contact temperature, which is expressed, not only through the thermal effusivities of the solid and liquid materials and their initial temperature, but also depends on the Prandtl number. The theory predicts a constant value of the contact temperature in the phase when the thermal boundary layer is thinner than the thickness of the lamella. The model is validated by comparison with the experimental data. The agreement is rather good despite the fact that no adjustable parameters are introduced in the model.
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Darbandi, Masoud, Rasool Khaledi-Alidusti, Moslem Sabouri, and Hossein Reza Abbasi. "A Molecular Dynamics Study of Fluid Flows Through Slit-Like Nanochannels Using Two Different Driving Systems." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31066.
Full textAbstract:
The Poiseuille flow through slit-like nanochannels is investigated using the nonequilibrium molecular dynamics simulations. To drive a dense flow through the channel, we use two self-adjusting vertical plates strategy. These plates force the liquid to flow through the nanochannel under adjustable inlet and outlet boundary conditions. Comparing with the dual-control-volume grand-canonical molecular dynamics method, the current strategy provides many advantages. The current strategy does not need particle insertion and deletion, therefore, the system dynamics would not be affected at all. Moreover, the number of particles in the simulation system is fixed due to inserting the two self-adjusting vertical plates at the two ends of the nanochannel. The motion of these plates are controlled using a combination of an externally applied force and an internal force produced by the molecules in the system. Using this strategy, we study the transport of liquid argon and oxygen through a few slit-like nanochannels having different sizes. We benefit from the nonequilibrium molecular dynamics (NEMD) strategy in our simulations. To expand our study, we consider different back pressure implementations in the flow through the nanochannel. The current results are eventually compared with those derived by applying a uniform driving force method and their advantages are described.